The operation of such an industrial machine can be simulated. If the industrial machine is a processing machine for processing a workpiece, when a workpiece is designed, not only technological and geometric but also qualitative parameters are advantageously defined. The determination of and testing for compliance with the qualitative parameters can be carried out during or after fabrication. The scope and time of this monitoring can be arranged, for example, according to technological or economic requirements. However, as a rule it is advantageous to determine deviation of actual variables with respect to setpoint variables at an early time so that in particular relatively high subsequent costs such as post-processing or total loss of the workpiece can be avoided. In order to monitor technological, geometric or else qualitative parameters, operations are usually carried out with a quality assurance process. This process accompanies, for example, the definition, the design and the fabrication of a workpiece. In this way it is possible, for example, to create a specification which defines which parameters (technological, geometric . . . ) are relevant to the quality of a workpiece, and in what way these parameters are to be monitored and documented. The greater the number of parameters which are monitored, the greater the expenditure required.
In order to ensure compliance with the abovementioned parameters, as a rule, measurements are carried out at specific times during or after a production process. Such a measurement relates, for example, also to the surface quality or to a tolerance value of a geometric dimension. Quality assurance consequently often takes place in subsequent process steps on machines which are specially provided for this purpose, which involves a corresponding high level of complexity and costs. A customary procedure is for process data to be obtained from the fabrication of a workpiece and for its quality to be checked by measurements. During the processing of further identical parts (workpieces), the process data which is then measured can be compared continuously with the data of the satisfactory part. It is thus possible to determine deviations from setpoint variables at an early time. However, this procedure is laborious and very time-consuming.
The operation of the industrial machine also relates, in particular, to the processing of a workpiece on a numerically-controlled processing machine. A computer numerically-controlled processing machine (CNC machine) is also understood to be a numerically-controlled processing machine in this context, and the processing machine can be a machine tool. Two or more processing steps can be provided for the processing of the workpiece. A method for processing a workpiece thus also includes a simulation method for three-dimensional processing by a CNC-controlled processing machine, in particular a milling machine and a descriptive data record which is necessary for this purpose.
In numerically-controlled processing machines, such as in particular CNC-controlled processing machines, a workpiece is either encoded directly by a programmer or the workpiece is modeled by means of a CAD system and then converted into an equivalent CNC parts program. The CNC parts program or the CAD model corresponds here to idealized processing instructions for the processing machine. The CNC program is loaded into a CNC controller and the processing machine is controlled in accordance with the CNC program. If the workpiece which is fabricated in this way lies within the desired fabrication tolerances of an ideal workpiece, no problems occur with this procedure. If, on the other hand, the fabricated workpiece does not correspond to the requirements, the question arises as to which variations are to be used for the fabrication of a satisfactory workpiece.
In order to correct faults, it is possible for individual processing instructions and/or individual operating parameters of the processing machine to be changed successively, for a new workpiece to be fabricated and then for this newly fabricated workpiece to be checked, but this procedure is very awkward and also costly, material-intensive and time-intensive. This applies particularly also because it is often not known where to look for the cause of the deviations of the actually fabricated workpiece from the desired workpiece.
EP 0879675 discloses a simulation method for NC machining on the basis of a shape of a workpiece, a shape of a tool and an NC program, which is intended to achieve feed forward control and optimum cutting conditions, and DE 10311027 discloses a measuring and simulation system for machine tools or production machines which simultaneously visualizes measurement and simulation results on a common screen, in which case an operator has to perform the subsequent comparison of the measurement and simulation results.
U.S. Pat. No. 5,208,763 specifies a machine tool which is equipped with sensors and which has a data processing system which transmits the position and orientation of a workpiece with respect to a model of the workpiece by means of coordinates of surface points which are determined on the workpiece. On this basis, a transformation of the workpiece is determined and said transformation is intended to produce a smaller difference between the relative spatial coordinates of the workpiece and of the model.
When particularly complex parts are fabricated, in particular in the case of parts with a large volume of removed material, as occurs, for example, in aircraft manufacture or else in turbine manufacture for power plants, a plurality of process steps with different tools are required. Since there is no CAD model for the individual subprocesses for manufacturing a part, the part being a workpiece, it is not possible at present to measure the quality of the subprocesses directly. Only the result of the overall process can be measured on a measuring machine or else on the fabrication machine. This means that even faults which have already occurred in the first process step can always only be detected after the fabrication of the entire part, for example a turbine blade. This procedure can lead, for example, to the following problems:                Parts/workpieces are always fabricated in a finished state even if an irreparable damage has occurred to the part even just after the start of the fabrication and has not been detected. As a result, valuable machine time is wasted;        the previously customary measuring of parts on a measuring machine is very cost-intensive since, on the one hand, the measuring machines for large parts are very expensive, and on the other hand the clamping of the in some cases very large workpieces on the measuring machine is extremely laborious;        faults in the production are often detected only weeks after the fabrication of parts, with the result that under certain circumstances an entire series of parts has been fabricated with faults during this time;        faults which were detected in a previously known way can be assigned unambiguously to a subprocess only in the rarest cases so that the correction of faults is in turn very laborious because all the subprocesses have to be examined.        